drivers/base/dd.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * drivers/base/dd.c - The core device/driver interactions.
   4  *
   5  * This file contains the (sometimes tricky) code that controls the
   6  * interactions between devices and drivers, which primarily includes
   7  * driver binding and unbinding.
   8  *
   9  * All of this code used to exist in drivers/base/bus.c, but was
  10  * relocated to here in the name of compartmentalization (since it wasn't
  11  * strictly code just for the 'struct bus_type'.
  12  *
  13  * Copyright (c) 2002-5 Patrick Mochel
  14  * Copyright (c) 2002-3 Open Source Development Labs
  15  * Copyright (c) 2007-2009 Greg Kroah-Hartman <gregkh@suse.de>
  16  * Copyright (c) 2007-2009 Novell Inc.
  17  */
  18
  19 #include <linux/debugfs.h>
  20 #include <linux/device.h>
  21 #include <linux/delay.h>
  22 #include <linux/dma-mapping.h>
  23 #include <linux/init.h>
  24 #include <linux/module.h>
  25 #include <linux/kthread.h>
  26 #include <linux/wait.h>
  27 #include <linux/async.h>
  28 #include <linux/pm_runtime.h>
  29 #include <linux/pinctrl/devinfo.h>
  30
  31 #include "base.h"
  32 #include "power/power.h"
  33
  34 /*
  35  * Deferred Probe infrastructure.
  36  *
  37  * Sometimes driver probe order matters, but the kernel doesn't always have
  38  * dependency information which means some drivers will get probed before a
  39  * resource it depends on is available.  For example, an SDHCI driver may
  40  * first need a GPIO line from an i2c GPIO controller before it can be
  41  * initialized.  If a required resource is not available yet, a driver can
  42  * request probing to be deferred by returning -EPROBE_DEFER from its probe hook
  43  *
  44  * Deferred probe maintains two lists of devices, a pending list and an active
  45  * list.  A driver returning -EPROBE_DEFER causes the device to be added to the
  46  * pending list.  A successful driver probe will trigger moving all devices
  47  * from the pending to the active list so that the workqueue will eventually
  48  * retry them.
  49  *
  50  * The deferred_probe_mutex must be held any time the deferred_probe_*_list
  51  * of the (struct device*)->p->deferred_probe pointers are manipulated
  52  */
  53 static DEFINE_MUTEX(deferred_probe_mutex);
  54 static LIST_HEAD(deferred_probe_pending_list);
  55 static LIST_HEAD(deferred_probe_active_list);
  56 static atomic_t deferred_trigger_count = ATOMIC_INIT(0);
  57 static struct dentry *deferred_devices;
  58 static bool initcalls_done;
  59
  60 /* Save the async probe drivers' name from kernel cmdline */
  61 #define ASYNC_DRV_NAMES_MAX_LEN 256
  62 static char async_probe_drv_names[ASYNC_DRV_NAMES_MAX_LEN];
  63
  64 /*
  65  * In some cases, like suspend to RAM or hibernation, It might be reasonable
  66  * to prohibit probing of devices as it could be unsafe.
  67  * Once defer_all_probes is true all drivers probes will be forcibly deferred.
  68  */
  69 static bool defer_all_probes;
  70
  71 /*
  72  * deferred_probe_work_func() - Retry probing devices in the active list.
  73  */
  74 static void deferred_probe_work_func(struct work_struct *work)
  75 {
  76         struct device *dev;
  77         struct device_private *private;
  78         /*
  79          * This block processes every device in the deferred 'active' list.
  80          * Each device is removed from the active list and passed to
  81          * bus_probe_device() to re-attempt the probe.  The loop continues
  82          * until every device in the active list is removed and retried.
  83          *
  84          * Note: Once the device is removed from the list and the mutex is
  85          * released, it is possible for the device get freed by another thread
  86          * and cause a illegal pointer dereference.  This code uses
  87          * get/put_device() to ensure the device structure cannot disappear
  88          * from under our feet.
  89          */
  90         mutex_lock(&deferred_probe_mutex);
  91         while (!list_empty(&deferred_probe_active_list)) {
  92                 private = list_first_entry(&deferred_probe_active_list,
  93                                         typeof(*dev->p), deferred_probe);
  94                 dev = private->device;
  95                 list_del_init(&private->deferred_probe);
  96
  97                 get_device(dev);
  98
  99                 /*
 100                  * Drop the mutex while probing each device; the probe path may
 101                  * manipulate the deferred list
 102                  */
 103                 mutex_unlock(&deferred_probe_mutex);
 104
 105                 /*
 106                  * Force the device to the end of the dpm_list since
 107                  * the PM code assumes that the order we add things to
 108                  * the list is a good order for suspend but deferred
 109                  * probe makes that very unsafe.
 110                  */
 111                 device_pm_move_to_tail(dev);
 112
 113                 dev_dbg(dev, "Retrying from deferred list\n");
 114                 bus_probe_device(dev);
 115                 mutex_lock(&deferred_probe_mutex);
 116
 117                 put_device(dev);
 118         }
 119         mutex_unlock(&deferred_probe_mutex);
 120 }
 121 static DECLARE_WORK(deferred_probe_work, deferred_probe_work_func);
 122
 123 void driver_deferred_probe_add(struct device *dev)
 124 {
 125         mutex_lock(&deferred_probe_mutex);
 126         if (list_empty(&dev->p->deferred_probe)) {
 127                 dev_dbg(dev, "Added to deferred list\n");
 128                 list_add_tail(&dev->p->deferred_probe, &deferred_probe_pending_list);
 129         }
 130         mutex_unlock(&deferred_probe_mutex);
 131 }
 132
 133 void driver_deferred_probe_del(struct device *dev)
 134 {
 135         mutex_lock(&deferred_probe_mutex);
 136         if (!list_empty(&dev->p->deferred_probe)) {
 137                 dev_dbg(dev, "Removed from deferred list\n");
 138                 list_del_init(&dev->p->deferred_probe);
 139         }
 140         mutex_unlock(&deferred_probe_mutex);
 141 }
 142
 143 static bool driver_deferred_probe_enable = false;
 144 /**
 145  * driver_deferred_probe_trigger() - Kick off re-probing deferred devices
 146  *
 147  * This functions moves all devices from the pending list to the active
 148  * list and schedules the deferred probe workqueue to process them.  It
 149  * should be called anytime a driver is successfully bound to a device.
 150  *
 151  * Note, there is a race condition in multi-threaded probe. In the case where
 152  * more than one device is probing at the same time, it is possible for one
 153  * probe to complete successfully while another is about to defer. If the second
 154  * depends on the first, then it will get put on the pending list after the
 155  * trigger event has already occurred and will be stuck there.
 156  *
 157  * The atomic 'deferred_trigger_count' is used to determine if a successful
 158  * trigger has occurred in the midst of probing a driver. If the trigger count
 159  * changes in the midst of a probe, then deferred processing should be triggered
 160  * again.
 161  */
 162 static void driver_deferred_probe_trigger(void)
 163 {
 164         if (!driver_deferred_probe_enable)
 165                 return;
 166
 167         /*
 168          * A successful probe means that all the devices in the pending list
 169          * should be triggered to be reprobed.  Move all the deferred devices
 170          * into the active list so they can be retried by the workqueue
 171          */
 172         mutex_lock(&deferred_probe_mutex);
 173         atomic_inc(&deferred_trigger_count);
 174         list_splice_tail_init(&deferred_probe_pending_list,
 175                               &deferred_probe_active_list);
 176         mutex_unlock(&deferred_probe_mutex);
 177
 178         /*
 179          * Kick the re-probe thread.  It may already be scheduled, but it is
 180          * safe to kick it again.
 181          */
 182         schedule_work(&deferred_probe_work);
 183 }
 184
 185 /**
 186  * device_block_probing() - Block/defer device's probes
 187  *
 188  *      It will disable probing of devices and defer their probes instead.
 189  */
 190 void device_block_probing(void)
 191 {
 192         defer_all_probes = true;
 193         /* sync with probes to avoid races. */
 194         wait_for_device_probe();
 195 }
 196
 197 /**
 198  * device_unblock_probing() - Unblock/enable device's probes
 199  *
 200  *      It will restore normal behavior and trigger re-probing of deferred
 201  * devices.
 202  */
 203 void device_unblock_probing(void)
 204 {
 205         defer_all_probes = false;
 206         driver_deferred_probe_trigger();
 207 }
 208
 209 /*
 210  * deferred_devs_show() - Show the devices in the deferred probe pending list.
 211  */
 212 static int deferred_devs_show(struct seq_file *s, void *data)
 213 {
 214         struct device_private *curr;
 215
 216         mutex_lock(&deferred_probe_mutex);
 217
 218         list_for_each_entry(curr, &deferred_probe_pending_list, deferred_probe)
 219                 seq_printf(s, "%s\n", dev_name(curr->device));
 220
 221         mutex_unlock(&deferred_probe_mutex);
 222
 223         return 0;
 224 }
 225 DEFINE_SHOW_ATTRIBUTE(deferred_devs);
 226
 227 static int deferred_probe_timeout = -1;
 228 static int __init deferred_probe_timeout_setup(char *str)
 229 {
 230         int timeout;
 231
 232         if (!kstrtoint(str, 10, &timeout))
 233                 deferred_probe_timeout = timeout;
 234         return 1;
 235 }
 236 __setup("deferred_probe_timeout=", deferred_probe_timeout_setup);
 237
 238 static int __driver_deferred_probe_check_state(struct device *dev)
 239 {
 240         if (!initcalls_done)
 241                 return -EPROBE_DEFER;
 242
 243         if (!deferred_probe_timeout) {
 244                 dev_WARN(dev, "deferred probe timeout, ignoring dependency");
 245                 return -ETIMEDOUT;
 246         }
 247
 248         return 0;
 249 }
 250
 251 /**
 252  * driver_deferred_probe_check_state() - Check deferred probe state
 253  * @dev: device to check
 254  *
 255  * Returns -ENODEV if init is done and all built-in drivers have had a chance
 256  * to probe (i.e. initcalls are done), -ETIMEDOUT if deferred probe debug
 257  * timeout has expired, or -EPROBE_DEFER if none of those conditions are met.
 258  *
 259  * Drivers or subsystems can opt-in to calling this function instead of directly
 260  * returning -EPROBE_DEFER.
 261  */
 262 int driver_deferred_probe_check_state(struct device *dev)
 263 {
 264         int ret;
 265
 266         ret = __driver_deferred_probe_check_state(dev);
 267         if (ret < 0)
 268                 return ret;
 269
 270         dev_warn(dev, "ignoring dependency for device, assuming no driver");
 271
 272         return -ENODEV;
 273 }
 274
 275 /**
 276  * driver_deferred_probe_check_state_continue() - check deferred probe state
 277  * @dev: device to check
 278  *
 279  * Returns -ETIMEDOUT if deferred probe debug timeout has expired, or
 280  * -EPROBE_DEFER otherwise.
 281  *
 282  * Drivers or subsystems can opt-in to calling this function instead of
 283  * directly returning -EPROBE_DEFER.
 284  *
 285  * This is similar to driver_deferred_probe_check_state(), but it allows the
 286  * subsystem to keep deferring probe after built-in drivers have had a chance
 287  * to probe. One scenario where that is useful is if built-in drivers rely on
 288  * resources that are provided by modular drivers.
 289  */
 290 int driver_deferred_probe_check_state_continue(struct device *dev)
 291 {
 292         int ret;
 293
 294         ret = __driver_deferred_probe_check_state(dev);
 295         if (ret < 0)
 296                 return ret;
 297
 298         return -EPROBE_DEFER;
 299 }
 300
 301 static void deferred_probe_timeout_work_func(struct work_struct *work)
 302 {
 303         struct device_private *private, *p;
 304
 305         deferred_probe_timeout = 0;
 306         driver_deferred_probe_trigger();
 307         flush_work(&deferred_probe_work);
 308
 309         list_for_each_entry_safe(private, p, &deferred_probe_pending_list, deferred_probe)
 310                 dev_info(private->device, "deferred probe pending");
 311 }
 312 static DECLARE_DELAYED_WORK(deferred_probe_timeout_work, deferred_probe_timeout_work_func);
 313
 314 /**
 315  * deferred_probe_initcall() - Enable probing of deferred devices
 316  *
 317  * We don't want to get in the way when the bulk of drivers are getting probed.
 318  * Instead, this initcall makes sure that deferred probing is delayed until
 319  * late_initcall time.
 320  */
 321 static int deferred_probe_initcall(void)
 322 {
 323         deferred_devices = debugfs_create_file("devices_deferred", 0444, NULL,
 324                                                NULL, &deferred_devs_fops);
 325
 326         driver_deferred_probe_enable = true;
 327         driver_deferred_probe_trigger();
 328         /* Sort as many dependencies as possible before exiting initcalls */
 329         flush_work(&deferred_probe_work);
 330         initcalls_done = true;
 331
 332         /*
 333          * Trigger deferred probe again, this time we won't defer anything
 334          * that is optional
 335          */
 336         driver_deferred_probe_trigger();
 337         flush_work(&deferred_probe_work);
 338
 339         if (deferred_probe_timeout > 0) {
 340                 schedule_delayed_work(&deferred_probe_timeout_work,
 341                         deferred_probe_timeout * HZ);
 342         }
 343         return 0;
 344 }
 345 late_initcall(deferred_probe_initcall);
 346
 347 static void __exit deferred_probe_exit(void)
 348 {
 349         debugfs_remove_recursive(deferred_devices);
 350 }
 351 __exitcall(deferred_probe_exit);
 352
 353 /**
 354  * device_is_bound() - Check if device is bound to a driver
 355  * @dev: device to check
 356  *
 357  * Returns true if passed device has already finished probing successfully
 358  * against a driver.
 359  *
 360  * This function must be called with the device lock held.
 361  */
 362 bool device_is_bound(struct device *dev)
 363 {
 364         return dev->p && klist_node_attached(&dev->p->knode_driver);
 365 }
 366
 367 static void driver_bound(struct device *dev)
 368 {
 369         if (device_is_bound(dev)) {
 370                 printk(KERN_WARNING "%s: device %s already bound\n",
 371                         __func__, kobject_name(&dev->kobj));
 372                 return;
 373         }
 374
 375         pr_debug("driver: '%s': %s: bound to device '%s'\n", dev->driver->name,
 376                  __func__, dev_name(dev));
 377
 378         klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices);
 379         device_links_driver_bound(dev);
 380
 381         device_pm_check_callbacks(dev);
 382
 383         /*
 384          * Make sure the device is no longer in one of the deferred lists and
 385          * kick off retrying all pending devices
 386          */
 387         driver_deferred_probe_del(dev);
 388         driver_deferred_probe_trigger();
 389
 390         if (dev->bus)
 391                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 392                                              BUS_NOTIFY_BOUND_DRIVER, dev);
 393
 394         kobject_uevent(&dev->kobj, KOBJ_BIND);
 395 }
 396
 397 static ssize_t coredump_store(struct device *dev, struct device_attribute *attr,
 398                             const char *buf, size_t count)
 399 {
 400         device_lock(dev);
 401         dev->driver->coredump(dev);
 402         device_unlock(dev);
 403
 404         return count;
 405 }
 406 static DEVICE_ATTR_WO(coredump);
 407
 408 static int driver_sysfs_add(struct device *dev)
 409 {
 410         int ret;
 411
 412         if (dev->bus)
 413                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 414                                              BUS_NOTIFY_BIND_DRIVER, dev);
 415
 416         ret = sysfs_create_link(&dev->driver->p->kobj, &dev->kobj,
 417                                 kobject_name(&dev->kobj));
 418         if (ret)
 419                 goto fail;
 420
 421         ret = sysfs_create_link(&dev->kobj, &dev->driver->p->kobj,
 422                                 "driver");
 423         if (ret)
 424                 goto rm_dev;
 425
 426         if (!IS_ENABLED(CONFIG_DEV_COREDUMP) || !dev->driver->coredump ||
 427             !device_create_file(dev, &dev_attr_coredump))
 428                 return 0;
 429
 430         sysfs_remove_link(&dev->kobj, "driver");
 431
 432 rm_dev:
 433         sysfs_remove_link(&dev->driver->p->kobj,
 434                           kobject_name(&dev->kobj));
 435
 436 fail:
 437         return ret;
 438 }
 439
 440 static void driver_sysfs_remove(struct device *dev)
 441 {
 442         struct device_driver *drv = dev->driver;
 443
 444         if (drv) {
 445                 if (drv->coredump)
 446                         device_remove_file(dev, &dev_attr_coredump);
 447                 sysfs_remove_link(&drv->p->kobj, kobject_name(&dev->kobj));
 448                 sysfs_remove_link(&dev->kobj, "driver");
 449         }
 450 }
 451
 452 /**
 453  * device_bind_driver - bind a driver to one device.
 454  * @dev: device.
 455  *
 456  * Allow manual attachment of a driver to a device.
 457  * Caller must have already set @dev->driver.
 458  *
 459  * Note that this does not modify the bus reference count
 460  * nor take the bus's rwsem. Please verify those are accounted
 461  * for before calling this. (It is ok to call with no other effort
 462  * from a driver's probe() method.)
 463  *
 464  * This function must be called with the device lock held.
 465  */
 466 int device_bind_driver(struct device *dev)
 467 {
 468         int ret;
 469
 470         ret = driver_sysfs_add(dev);
 471         if (!ret)
 472                 driver_bound(dev);
 473         else if (dev->bus)
 474                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 475                                              BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
 476         return ret;
 477 }
 478 EXPORT_SYMBOL_GPL(device_bind_driver);
 479
 480 static atomic_t probe_count = ATOMIC_INIT(0);
 481 static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
 482
 483 static void driver_deferred_probe_add_trigger(struct device *dev,
 484                                               int local_trigger_count)
 485 {
 486         driver_deferred_probe_add(dev);
 487         /* Did a trigger occur while probing? Need to re-trigger if yes */
 488         if (local_trigger_count != atomic_read(&deferred_trigger_count))
 489                 driver_deferred_probe_trigger();
 490 }
 491
 492 static int really_probe(struct device *dev, struct device_driver *drv)
 493 {
 494         int ret = -EPROBE_DEFER;
 495         int local_trigger_count = atomic_read(&deferred_trigger_count);
 496         bool test_remove = IS_ENABLED(CONFIG_DEBUG_TEST_DRIVER_REMOVE) &&
 497                            !drv->suppress_bind_attrs;
 498
 499         if (defer_all_probes) {
 500                 /*
 501                  * Value of defer_all_probes can be set only by
 502                  * device_block_probing() which, in turn, will call
 503                  * wait_for_device_probe() right after that to avoid any races.
 504                  */
 505                 dev_dbg(dev, "Driver %s force probe deferral\n", drv->name);
 506                 driver_deferred_probe_add(dev);
 507                 return ret;
 508         }
 509
 510         ret = device_links_check_suppliers(dev);
 511         if (ret == -EPROBE_DEFER)
 512                 driver_deferred_probe_add_trigger(dev, local_trigger_count);
 513         if (ret)
 514                 return ret;
 515
 516         atomic_inc(&probe_count);
 517         pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
 518                  drv->bus->name, __func__, drv->name, dev_name(dev));
 519         WARN_ON(!list_empty(&dev->devres_head));
 520
 521 re_probe:
 522         dev->driver = drv;
 523
 524         /* If using pinctrl, bind pins now before probing */
 525         ret = pinctrl_bind_pins(dev);
 526         if (ret)
 527                 goto pinctrl_bind_failed;
 528
 529         if (dev->bus->dma_configure) {
 530                 ret = dev->bus->dma_configure(dev);
 531                 if (ret)
 532                         goto probe_failed;
 533         }
 534
 535         if (driver_sysfs_add(dev)) {
 536                 printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
 537                         __func__, dev_name(dev));
 538                 goto probe_failed;
 539         }
 540
 541         if (dev->pm_domain && dev->pm_domain->activate) {
 542                 ret = dev->pm_domain->activate(dev);
 543                 if (ret)
 544                         goto probe_failed;
 545         }
 546
 547         if (dev->bus->probe) {
 548                 ret = dev->bus->probe(dev);
 549                 if (ret)
 550                         goto probe_failed;
 551         } else if (drv->probe) {
 552                 ret = drv->probe(dev);
 553                 if (ret)
 554                         goto probe_failed;
 555         }
 556
 557         if (device_add_groups(dev, drv->dev_groups)) {
 558                 dev_err(dev, "device_add_groups() failed\n");
 559                 goto dev_groups_failed;
 560         }
 561
 562         if (test_remove) {
 563                 test_remove = false;
 564
 565                 device_remove_groups(dev, drv->dev_groups);
 566
 567                 if (dev->bus->remove)
 568                         dev->bus->remove(dev);
 569                 else if (drv->remove)
 570                         drv->remove(dev);
 571
 572                 devres_release_all(dev);
 573                 driver_sysfs_remove(dev);
 574                 dev->driver = NULL;
 575                 dev_set_drvdata(dev, NULL);
 576                 if (dev->pm_domain && dev->pm_domain->dismiss)
 577                         dev->pm_domain->dismiss(dev);
 578                 pm_runtime_reinit(dev);
 579
 580                 goto re_probe;
 581         }
 582
 583         pinctrl_init_done(dev);
 584
 585         if (dev->pm_domain && dev->pm_domain->sync)
 586                 dev->pm_domain->sync(dev);
 587
 588         driver_bound(dev);
 589         ret = 1;
 590         pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
 591                  drv->bus->name, __func__, dev_name(dev), drv->name);
 592         goto done;
 593
 594 dev_groups_failed:
 595         if (dev->bus->remove)
 596                 dev->bus->remove(dev);
 597         else if (drv->remove)
 598                 drv->remove(dev);
 599 probe_failed:
 600         if (dev->bus)
 601                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 602                                              BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
 603 pinctrl_bind_failed:
 604         device_links_no_driver(dev);
 605         devres_release_all(dev);
 606         arch_teardown_dma_ops(dev);
 607         driver_sysfs_remove(dev);
 608         dev->driver = NULL;
 609         dev_set_drvdata(dev, NULL);
 610         if (dev->pm_domain && dev->pm_domain->dismiss)
 611                 dev->pm_domain->dismiss(dev);
 612         pm_runtime_reinit(dev);
 613         dev_pm_set_driver_flags(dev, 0);
 614
 615         switch (ret) {
 616         case -EPROBE_DEFER:
 617                 /* Driver requested deferred probing */
 618                 dev_dbg(dev, "Driver %s requests probe deferral\n", drv->name);
 619                 driver_deferred_probe_add_trigger(dev, local_trigger_count);
 620                 break;
 621         case -ENODEV:
 622         case -ENXIO:
 623                 pr_debug("%s: probe of %s rejects match %d\n",
 624                          drv->name, dev_name(dev), ret);
 625                 break;
 626         default:
 627                 /* driver matched but the probe failed */
 628                 printk(KERN_WARNING
 629                        "%s: probe of %s failed with error %d\n",
 630                        drv->name, dev_name(dev), ret);
 631         }
 632         /*
 633          * Ignore errors returned by ->probe so that the next driver can try
 634          * its luck.
 635          */
 636         ret = 0;
 637 done:
 638         atomic_dec(&probe_count);
 639         wake_up(&probe_waitqueue);
 640         return ret;
 641 }
 642
 643 /*
 644  * For initcall_debug, show the driver probe time.
 645  */
 646 static int really_probe_debug(struct device *dev, struct device_driver *drv)
 647 {
 648         ktime_t calltime, delta, rettime;
 649         int ret;
 650
 651         calltime = ktime_get();
 652         ret = really_probe(dev, drv);
 653         rettime = ktime_get();
 654         delta = ktime_sub(rettime, calltime);
 655         printk(KERN_DEBUG "probe of %s returned %d after %lld usecs\n",
 656                dev_name(dev), ret, (s64) ktime_to_us(delta));
 657         return ret;
 658 }
 659
 660 /**
 661  * driver_probe_done
 662  * Determine if the probe sequence is finished or not.
 663  *
 664  * Should somehow figure out how to use a semaphore, not an atomic variable...
 665  */
 666 int driver_probe_done(void)
 667 {
 668         pr_debug("%s: probe_count = %d\n", __func__,
 669                  atomic_read(&probe_count));
 670         if (atomic_read(&probe_count))
 671                 return -EBUSY;
 672         return 0;
 673 }
 674
 675 /**
 676  * wait_for_device_probe
 677  * Wait for device probing to be completed.
 678  */
 679 void wait_for_device_probe(void)
 680 {
 681         /* wait for the deferred probe workqueue to finish */
 682         flush_work(&deferred_probe_work);
 683
 684         /* wait for the known devices to complete their probing */
 685         wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
 686         async_synchronize_full();
 687 }
 688 EXPORT_SYMBOL_GPL(wait_for_device_probe);
 689
 690 /**
 691  * driver_probe_device - attempt to bind device & driver together
 692  * @drv: driver to bind a device to
 693  * @dev: device to try to bind to the driver
 694  *
 695  * This function returns -ENODEV if the device is not registered,
 696  * 1 if the device is bound successfully and 0 otherwise.
 697  *
 698  * This function must be called with @dev lock held.  When called for a
 699  * USB interface, @dev->parent lock must be held as well.
 700  *
 701  * If the device has a parent, runtime-resume the parent before driver probing.
 702  */
 703 int driver_probe_device(struct device_driver *drv, struct device *dev)
 704 {
 705         int ret = 0;
 706
 707         if (!device_is_registered(dev))
 708                 return -ENODEV;
 709
 710         pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
 711                  drv->bus->name, __func__, dev_name(dev), drv->name);
 712
 713         pm_runtime_get_suppliers(dev);
 714         if (dev->parent)
 715                 pm_runtime_get_sync(dev->parent);
 716
 717         pm_runtime_barrier(dev);
 718         if (initcall_debug)
 719                 ret = really_probe_debug(dev, drv);
 720         else
 721                 ret = really_probe(dev, drv);
 722         pm_request_idle(dev);
 723
 724         if (dev->parent)
 725                 pm_runtime_put(dev->parent);
 726
 727         pm_runtime_put_suppliers(dev);
 728         return ret;
 729 }
 730
 731 static inline bool cmdline_requested_async_probing(const char *drv_name)
 732 {
 733         return parse_option_str(async_probe_drv_names, drv_name);
 734 }
 735
 736 /* The option format is "driver_async_probe=drv_name1,drv_name2,..." */
 737 static int __init save_async_options(char *buf)
 738 {
 739         if (strlen(buf) >= ASYNC_DRV_NAMES_MAX_LEN)
 740                 printk(KERN_WARNING
 741                         "Too long list of driver names for 'driver_async_probe'!\n");
 742
 743         strlcpy(async_probe_drv_names, buf, ASYNC_DRV_NAMES_MAX_LEN);
 744         return 0;
 745 }
 746 __setup("driver_async_probe=", save_async_options);
 747
 748 bool driver_allows_async_probing(struct device_driver *drv)
 749 {
 750         switch (drv->probe_type) {
 751         case PROBE_PREFER_ASYNCHRONOUS:
 752                 return true;
 753
 754         case PROBE_FORCE_SYNCHRONOUS:
 755                 return false;
 756
 757         default:
 758                 if (cmdline_requested_async_probing(drv->name))
 759                         return true;
 760
 761                 if (module_requested_async_probing(drv->owner))
 762                         return true;
 763
 764                 return false;
 765         }
 766 }
 767
 768 struct device_attach_data {
 769         struct device *dev;
 770
 771         /*
 772          * Indicates whether we are are considering asynchronous probing or
 773          * not. Only initial binding after device or driver registration
 774          * (including deferral processing) may be done asynchronously, the
 775          * rest is always synchronous, as we expect it is being done by
 776          * request from userspace.
 777          */
 778         bool check_async;
 779
 780         /*
 781          * Indicates if we are binding synchronous or asynchronous drivers.
 782          * When asynchronous probing is enabled we'll execute 2 passes
 783          * over drivers: first pass doing synchronous probing and second
 784          * doing asynchronous probing (if synchronous did not succeed -
 785          * most likely because there was no driver requiring synchronous
 786          * probing - and we found asynchronous driver during first pass).
 787          * The 2 passes are done because we can't shoot asynchronous
 788          * probe for given device and driver from bus_for_each_drv() since
 789          * driver pointer is not guaranteed to stay valid once
 790          * bus_for_each_drv() iterates to the next driver on the bus.
 791          */
 792         bool want_async;
 793
 794         /*
 795          * We'll set have_async to 'true' if, while scanning for matching
 796          * driver, we'll encounter one that requests asynchronous probing.
 797          */
 798         bool have_async;
 799 };
 800
 801 static int __device_attach_driver(struct device_driver *drv, void *_data)
 802 {
 803         struct device_attach_data *data = _data;
 804         struct device *dev = data->dev;
 805         bool async_allowed;
 806         int ret;
 807
 808         ret = driver_match_device(drv, dev);
 809         if (ret == 0) {
 810                 /* no match */
 811                 return 0;
 812         } else if (ret == -EPROBE_DEFER) {
 813                 dev_dbg(dev, "Device match requests probe deferral\n");
 814                 driver_deferred_probe_add(dev);
 815         } else if (ret < 0) {
 816                 dev_dbg(dev, "Bus failed to match device: %d", ret);
 817                 return ret;
 818         } /* ret > 0 means positive match */
 819
 820         async_allowed = driver_allows_async_probing(drv);
 821
 822         if (async_allowed)
 823                 data->have_async = true;
 824
 825         if (data->check_async && async_allowed != data->want_async)
 826                 return 0;
 827
 828         return driver_probe_device(drv, dev);
 829 }
 830
 831 static void __device_attach_async_helper(void *_dev, async_cookie_t cookie)
 832 {
 833         struct device *dev = _dev;
 834         struct device_attach_data data = {
 835                 .dev            = dev,
 836                 .check_async    = true,
 837                 .want_async     = true,
 838         };
 839
 840         device_lock(dev);
 841
 842         /*
 843          * Check if device has already been removed or claimed. This may
 844          * happen with driver loading, device discovery/registration,
 845          * and deferred probe processing happens all at once with
 846          * multiple threads.
 847          */
 848         if (dev->p->dead || dev->driver)
 849                 goto out_unlock;
 850
 851         if (dev->parent)
 852                 pm_runtime_get_sync(dev->parent);
 853
 854         bus_for_each_drv(dev->bus, NULL, &data, __device_attach_driver);
 855         dev_dbg(dev, "async probe completed\n");
 856
 857         pm_request_idle(dev);
 858
 859         if (dev->parent)
 860                 pm_runtime_put(dev->parent);
 861 out_unlock:
 862         device_unlock(dev);
 863
 864         put_device(dev);
 865 }
 866
 867 static int __device_attach(struct device *dev, bool allow_async)
 868 {
 869         int ret = 0;
 870
 871         device_lock(dev);
 872         if (dev->driver) {
 873                 if (device_is_bound(dev)) {
 874                         ret = 1;
 875                         goto out_unlock;
 876                 }
 877                 ret = device_bind_driver(dev);
 878                 if (ret == 0)
 879                         ret = 1;
 880                 else {
 881                         dev->driver = NULL;
 882                         ret = 0;
 883                 }
 884         } else {
 885                 struct device_attach_data data = {
 886                         .dev = dev,
 887                         .check_async = allow_async,
 888                         .want_async = false,
 889                 };
 890
 891                 if (dev->parent)
 892                         pm_runtime_get_sync(dev->parent);
 893
 894                 ret = bus_for_each_drv(dev->bus, NULL, &data,
 895                                         __device_attach_driver);
 896                 if (!ret && allow_async && data.have_async) {
 897                         /*
 898                          * If we could not find appropriate driver
 899                          * synchronously and we are allowed to do
 900                          * async probes and there are drivers that
 901                          * want to probe asynchronously, we'll
 902                          * try them.
 903                          */
 904                         dev_dbg(dev, "scheduling asynchronous probe\n");
 905                         get_device(dev);
 906                         async_schedule_dev(__device_attach_async_helper, dev);
 907                 } else {
 908                         pm_request_idle(dev);
 909                 }
 910
 911                 if (dev->parent)
 912                         pm_runtime_put(dev->parent);
 913         }
 914 out_unlock:
 915         device_unlock(dev);
 916         return ret;
 917 }
 918
 919 /**
 920  * device_attach - try to attach device to a driver.
 921  * @dev: device.
 922  *
 923  * Walk the list of drivers that the bus has and call
 924  * driver_probe_device() for each pair. If a compatible
 925  * pair is found, break out and return.
 926  *
 927  * Returns 1 if the device was bound to a driver;
 928  * 0 if no matching driver was found;
 929  * -ENODEV if the device is not registered.
 930  *
 931  * When called for a USB interface, @dev->parent lock must be held.
 932  */
 933 int device_attach(struct device *dev)
 934 {
 935         return __device_attach(dev, false);
 936 }
 937 EXPORT_SYMBOL_GPL(device_attach);
 938
 939 void device_initial_probe(struct device *dev)
 940 {
 941         __device_attach(dev, true);
 942 }
 943
 944 /*
 945  * __device_driver_lock - acquire locks needed to manipulate dev->drv
 946  * @dev: Device we will update driver info for
 947  * @parent: Parent device. Needed if the bus requires parent lock
 948  *
 949  * This function will take the required locks for manipulating dev->drv.
 950  * Normally this will just be the @dev lock, but when called for a USB
 951  * interface, @parent lock will be held as well.
 952  */
 953 static void __device_driver_lock(struct device *dev, struct device *parent)
 954 {
 955         if (parent && dev->bus->need_parent_lock)
 956                 device_lock(parent);
 957         device_lock(dev);
 958 }
 959
 960 /*
 961  * __device_driver_unlock - release locks needed to manipulate dev->drv
 962  * @dev: Device we will update driver info for
 963  * @parent: Parent device. Needed if the bus requires parent lock
 964  *
 965  * This function will release the required locks for manipulating dev->drv.
 966  * Normally this will just be the the @dev lock, but when called for a
 967  * USB interface, @parent lock will be released as well.
 968  */
 969 static void __device_driver_unlock(struct device *dev, struct device *parent)
 970 {
 971         device_unlock(dev);
 972         if (parent && dev->bus->need_parent_lock)
 973                 device_unlock(parent);
 974 }
 975
 976 /**
 977  * device_driver_attach - attach a specific driver to a specific device
 978  * @drv: Driver to attach
 979  * @dev: Device to attach it to
 980  *
 981  * Manually attach driver to a device. Will acquire both @dev lock and
 982  * @dev->parent lock if needed.
 983  */
 984 int device_driver_attach(struct device_driver *drv, struct device *dev)
 985 {
 986         int ret = 0;
 987
 988         __device_driver_lock(dev, dev->parent);
 989
 990         /*
 991          * If device has been removed or someone has already successfully
 992          * bound a driver before us just skip the driver probe call.
 993          */
 994         if (!dev->p->dead && !dev->driver)
 995                 ret = driver_probe_device(drv, dev);
 996
 997         __device_driver_unlock(dev, dev->parent);
 998
 999         return ret;
1000 }
1001
1002 static void __driver_attach_async_helper(void *_dev, async_cookie_t cookie)
1003 {
1004         struct device *dev = _dev;
1005         struct device_driver *drv;
1006         int ret = 0;
1007
1008         __device_driver_lock(dev, dev->parent);
1009
1010         drv = dev->p->async_driver;
1011
1012         /*
1013          * If device has been removed or someone has already successfully
1014          * bound a driver before us just skip the driver probe call.
1015          */
1016         if (!dev->p->dead && !dev->driver)
1017                 ret = driver_probe_device(drv, dev);
1018
1019         __device_driver_unlock(dev, dev->parent);
1020
1021         dev_dbg(dev, "driver %s async attach completed: %d\n", drv->name, ret);
1022
1023         put_device(dev);
1024 }
1025
1026 static int __driver_attach(struct device *dev, void *data)
1027 {
1028         struct device_driver *drv = data;
1029         int ret;
1030
1031         /*
1032          * Lock device and try to bind to it. We drop the error
1033          * here and always return 0, because we need to keep trying
1034          * to bind to devices and some drivers will return an error
1035          * simply if it didn't support the device.
1036          *
1037          * driver_probe_device() will spit a warning if there
1038          * is an error.
1039          */
1040
1041         ret = driver_match_device(drv, dev);
1042         if (ret == 0) {
1043                 /* no match */
1044                 return 0;
1045         } else if (ret == -EPROBE_DEFER) {
1046                 dev_dbg(dev, "Device match requests probe deferral\n");
1047                 driver_deferred_probe_add(dev);
1048         } else if (ret < 0) {
1049                 dev_dbg(dev, "Bus failed to match device: %d", ret);
1050                 return ret;
1051         } /* ret > 0 means positive match */
1052
1053         if (driver_allows_async_probing(drv)) {
1054                 /*
1055                  * Instead of probing the device synchronously we will
1056                  * probe it asynchronously to allow for more parallelism.
1057                  *
1058                  * We only take the device lock here in order to guarantee
1059                  * that the dev->driver and async_driver fields are protected
1060                  */
1061                 dev_dbg(dev, "probing driver %s asynchronously\n", drv->name);
1062                 device_lock(dev);
1063                 if (!dev->driver) {
1064                         get_device(dev);
1065                         dev->p->async_driver = drv;
1066                         async_schedule_dev(__driver_attach_async_helper, dev);
1067                 }
1068                 device_unlock(dev);
1069                 return 0;
1070         }
1071
1072         device_driver_attach(drv, dev);
1073
1074         return 0;
1075 }
1076
1077 /**
1078  * driver_attach - try to bind driver to devices.
1079  * @drv: driver.
1080  *
1081  * Walk the list of devices that the bus has on it and try to
1082  * match the driver with each one.  If driver_probe_device()
1083  * returns 0 and the @dev->driver is set, we've found a
1084  * compatible pair.
1085  */
1086 int driver_attach(struct device_driver *drv)
1087 {
1088         return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
1089 }
1090 EXPORT_SYMBOL_GPL(driver_attach);
1091
1092 /*
1093  * __device_release_driver() must be called with @dev lock held.
1094  * When called for a USB interface, @dev->parent lock must be held as well.
1095  */
1096 static void __device_release_driver(struct device *dev, struct device *parent)
1097 {
1098         struct device_driver *drv;
1099
1100         drv = dev->driver;
1101         if (drv) {
1102                 while (device_links_busy(dev)) {
1103                         __device_driver_unlock(dev, parent);
1104
1105                         device_links_unbind_consumers(dev);
1106
1107                         __device_driver_lock(dev, parent);
1108                         /*
1109                          * A concurrent invocation of the same function might
1110                          * have released the driver successfully while this one
1111                          * was waiting, so check for that.
1112                          */
1113                         if (dev->driver != drv)
1114                                 return;
1115                 }
1116
1117                 pm_runtime_get_sync(dev);
1118                 pm_runtime_clean_up_links(dev);
1119
1120                 driver_sysfs_remove(dev);
1121
1122                 if (dev->bus)
1123                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
1124                                                      BUS_NOTIFY_UNBIND_DRIVER,
1125                                                      dev);
1126
1127                 pm_runtime_put_sync(dev);
1128
1129                 device_remove_groups(dev, drv->dev_groups);
1130
1131                 if (dev->bus && dev->bus->remove)
1132                         dev->bus->remove(dev);
1133                 else if (drv->remove)
1134                         drv->remove(dev);
1135
1136                 device_links_driver_cleanup(dev);
1137
1138                 devres_release_all(dev);
1139                 arch_teardown_dma_ops(dev);
1140                 dev->driver = NULL;
1141                 dev_set_drvdata(dev, NULL);
1142                 if (dev->pm_domain && dev->pm_domain->dismiss)
1143                         dev->pm_domain->dismiss(dev);
1144                 pm_runtime_reinit(dev);
1145                 dev_pm_set_driver_flags(dev, 0);
1146
1147                 klist_remove(&dev->p->knode_driver);
1148                 device_pm_check_callbacks(dev);
1149                 if (dev->bus)
1150                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
1151                                                      BUS_NOTIFY_UNBOUND_DRIVER,
1152                                                      dev);
1153
1154                 kobject_uevent(&dev->kobj, KOBJ_UNBIND);
1155         }
1156 }
1157
1158 void device_release_driver_internal(struct device *dev,
1159                                     struct device_driver *drv,
1160                                     struct device *parent)
1161 {
1162         __device_driver_lock(dev, parent);
1163
1164         if (!drv || drv == dev->driver)
1165                 __device_release_driver(dev, parent);
1166
1167         __device_driver_unlock(dev, parent);
1168 }
1169
1170 /**
1171  * device_release_driver - manually detach device from driver.
1172  * @dev: device.
1173  *
1174  * Manually detach device from driver.
1175  * When called for a USB interface, @dev->parent lock must be held.
1176  *
1177  * If this function is to be called with @dev->parent lock held, ensure that
1178  * the device's consumers are unbound in advance or that their locks can be
1179  * acquired under the @dev->parent lock.
1180  */
1181 void device_release_driver(struct device *dev)
1182 {
1183         /*
1184          * If anyone calls device_release_driver() recursively from
1185          * within their ->remove callback for the same device, they
1186          * will deadlock right here.
1187          */
1188         device_release_driver_internal(dev, NULL, NULL);
1189 }
1190 EXPORT_SYMBOL_GPL(device_release_driver);
1191
1192 /**
1193  * device_driver_detach - detach driver from a specific device
1194  * @dev: device to detach driver from
1195  *
1196  * Detach driver from device. Will acquire both @dev lock and @dev->parent
1197  * lock if needed.
1198  */
1199 void device_driver_detach(struct device *dev)
1200 {
1201         device_release_driver_internal(dev, NULL, dev->parent);
1202 }
1203
1204 /**
1205  * driver_detach - detach driver from all devices it controls.
1206  * @drv: driver.
1207  */
1208 void driver_detach(struct device_driver *drv)
1209 {
1210         struct device_private *dev_prv;
1211         struct device *dev;
1212
1213         if (driver_allows_async_probing(drv))
1214                 async_synchronize_full();
1215
1216         for (;;) {
1217                 spin_lock(&drv->p->klist_devices.k_lock);
1218                 if (list_empty(&drv->p->klist_devices.k_list)) {
1219                         spin_unlock(&drv->p->klist_devices.k_lock);
1220                         break;
1221                 }
1222                 dev_prv = list_entry(drv->p->klist_devices.k_list.prev,
1223                                      struct device_private,
1224                                      knode_driver.n_node);
1225                 dev = dev_prv->device;
1226                 get_device(dev);
1227                 spin_unlock(&drv->p->klist_devices.k_lock);
1228                 device_release_driver_internal(dev, drv, dev->parent);
1229                 put_device(dev);
1230         }
1231 }